Display device and touch detection method of display device

ABSTRACT

According to one embodiment, a display device includes a plurality of gate lines, a plurality of data lines intersecting with the gate lines, a plurality of pixel electrodes, and a sensor drive controller which includes a plurality of common electrodes facing the pixel electrodes and detects a touch by controlling the common electrodes. The sensor drive controller selects at least one of the common electrodes, and supplies a sensor signal to the selected common electrode to set the selected common electrode to a sensing state. The sensor drive controller sets at least the common electrode adjacent to the common electrode set to the sensing state to a guard state and sets the other common electrodes to a floating state.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 15/395,097,filed Dec. 30, 2016, which is based upon and claims the benefit ofpriority from Japanese Patent Application No. 2016-046910, filed Mar.10, 2016, the entire contents of which are incorporated herein byreference.

FIELD

Embodiments described herein relate generally to a display device and atouch detection method of a display device.

BACKGROUND

In general, display devices which can be applied to mobile communicationterminals called smartphones or tablet computers can be operated bybringing a means for inputting data, such as a stylus or fingers, intocontact with a display surface which displays an image. These displaydevices include in-cell display devices in which a touch detectionfunction is partially or entirely incorporated into a display panel, andon-cell display devices in which a sensor having a touch detectionfunction is provided on the display surface of a display panel.

As the above in-cell display device having a touch detection function,the following structure is known. Sensor electrodes formed of atransparent conductive film such as indium tin oxide (ITO) or indiumzinc oxide (IZO) are provided in matrix in the display area whichdisplays an image. A detection circuit is provided so as to correspondto each sensor electrode. Further, the sensor electrodes are connectedto the detection circuits by thin metal lines.

However, the conventional display devices having a touch detectionfunction require the same number of detection circuits as the number ofsensor electrodes. Thus, it is difficult to respond to increase in thenumber of sensor electrodes caused by improvement of detectionperformance or by increase in the size of the display panel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows touch detection by a self-capacitive system.

FIG. 2 is a graph showing change in capacitance when a touch is detectedby a self-capacitive system.

FIG. 3 is a plan view schematically showing the structure of a liquidcrystal display device having a touch function according to a firstembodiment.

FIG. 4 is a plan view showing the pixel structure of the liquid crystaldisplay device having a touch function according to the firstembodiment.

FIG. 5 is a cross-sectional view showing the layer structure of theliquid crystal display device having a touch function along dashed lineX-X′ of FIG. 4 according to the first embodiment.

FIG. 6A is a plan view schematically showing the structure of acontroller provided in the liquid crystal display device having a touchfunction according to the first embodiment.

FIG. 6B is a plan view schematically showing structural elements whichcontribute to touch detection in the liquid crystal display devicehaving a touch function according to the first embodiment.

FIG. 7A is a plan view schematically showing the circuit structure of asensor drive controller provided in the liquid crystal display devicehaving a touch function according to the first embodiment.

FIG. 7B shows an example of relationships between sensor signal voltage,guard signal voltage and floating voltage in the liquid crystal displaydevice having a touch function according to the first embodiment.

FIG. 8 is a timing chart shown for explaining the sequence of drivingcommon electrodes in the liquid crystal display device having a touchfunction according to the first embodiment.

FIG. 9 is shown for explaining the general structure and operation of aswitch drive circuit usable in the first embodiment.

FIG. 10 is a plan view schematically showing the circuit structure of asensor drive controller provided in a liquid crystal display devicehaving a touch function according to a second embodiment.

FIG. 11 is a timing chart shown for explaining the sequence of drivingcommon electrodes in the liquid crystal display device having a touchfunction according to the second embodiment.

FIG. 12 is shown for explaining an example of the general structure andoperation of a switch drive circuit usable in the second embodiment.

FIG. 13 is a plan view schematically showing the circuit structure of amodification example of the liquid crystal display device having a touchfunction according to the first embodiment.

FIG. 14 is a plan view schematically showing the circuit structure of amodification example of the liquid crystal display device having a touchfunction according to the second embodiment.

FIG. 15 is a plan view schematically showing the circuit structure ofanother modification example of the liquid crystal display device havinga touch function according to the first embodiment.

FIG. 16 is a plan view schematically showing the circuit structure ofanother modification example of the liquid crystal display device havinga touch function according to the second embodiment.

FIG. 17 is an enlarged plan view schematically showing a part ofstructural examples of a black matrix 8 and a shielding portion 9 usablein each of the above embodiments.

DETAILED DESCRIPTION

The embodiments of the present invention provide a display device whichrealizes a decrease in the area of a detection circuit or an ICincluding the detection circuit and is advantageous in terms of powersaving and manufacturing, and a touch detection method of the displaydevice.

In general, according to one embodiment, a display device comprising:

a plurality of gate lines;

a plurality of data lines intersecting with the gate lines;

a plurality of pixel electrodes provided in areas defined by the gatelines and the data lines;

a plurality of common electrodes opposing to the pixel electrodes; and

a sensor drive controller controlling the common electrodes to detect atouch, wherein

the sensor drive controller comprises:

a switch drive circuit which selects at least one of the commonelectrodes for sensing, and selects the other common electrodes fornon-sensing;

a sensing circuit which supplies a sensor signal to the common electrodeselected for sensing; and

a common voltage drive circuit comprising a first switch, and the firstswitch setting at least one of the common electrodes selected fornon-sensing to a floating state.

According to another embodiment, a display device comprises:

a plurality of gate lines;

a plurality of data lines intersecting with the gate lines;

a plurality of pixel electrodes provided in areas defined by the gatelines and the data lines; and

a sensor drive controller which comprises a plurality of commonelectrodes facing the pixel electrodes, and detects a touch by using thecommon electrodes, wherein

the sensor drive controller selects at least one of the commonelectrodes, sets the selected common electrode as a sensor electrode ina sensing state, sets the selected other common electrodes as floatingelectrodes in a floating state, and further, selects the commonelectrode adjacent to the sensor electrode set to the sensing state as aguard electrode in a guard state.

According to yet another embodiment, a display device comprises:

a plurality of gate lines;

a plurality of data lines intersecting with the gate lines;

a plurality of pixel electrodes provided in areas defined by the gatelines and the data lines; and

a sensor drive controller which comprises a plurality of commonelectrodes facing the pixel electrodes, and detects a touch by using thecommon electrodes, wherein

the sensor drive controller selects at least one of the commonelectrodes as a sensor electrode set to a sensing state, and controlsthe sensor electrode by a self-capacitive system for inputting a sensorsignal to the sensor electrode and detecting change in the sensorsignal.

According to yet another embodiment, a display device comprises:

a plurality of gate lines;

a plurality of data lines intersecting with the gate lines;

a plurality of pixel electrodes provided in areas defined by the gatelines and the data lines; and

a sensor drive controller which comprises a plurality of commonelectrodes facing the pixel electrodes, and detects a touch by using thecommon electrodes, wherein

the sensor drive controller comprises at least one detection circuit fordetecting a touch, and a plurality of select circuits which selectivelyconnect the detection circuit and a specific common electrode.

According to one embodiment, in a touch detection method of a displaydevice, the display device comprises:

a plurality of gate lines;

a plurality of data lines intersecting with the gate lines;

a plurality of pixel electrodes provided in areas defined by the gatelines and the data lines; and

a plurality of common electrodes facing the pixel electrodes.

The method comprises:

selecting at least one of the common electrodes as a sensor electrodeset to a sensing state;

selecting at least the common electrode adjacent to the sensor electrodeset to the sensing state as a guard electrode set to a guard state; and

setting the selected other common electrodes as floating electrodes setto a floating state.

Embodiments will further be described with reference to the accompanyingdrawings.

The disclosure is merely an example, and proper changes in keeping withthe spirit of the invention, which are easily conceivable by a person ofordinary skill in the art, come within the scope of the invention as amatter of course. In addition, in some cases, in order to make thedescription clearer, the widths, thicknesses, shapes, etc., of therespective parts are illustrated schematically in the drawings, ratherthan as an accurate representation of what is implemented. However, suchschematic illustration is merely exemplary, and in no way restricts theinterpretation of the invention. In addition, in the specification anddrawings, the same elements as those described in connection withpreceding drawings are denoted by like reference numbers, and detaileddescription thereof is omitted unless necessary.

(Touch Detection by Self-Capacitive System)

This specification explains the basic principle of touch detection by aself-capacitive system in a display device having a touch detectionfunction according to each embodiment of the present invention.

FIG. 1 schematically shows touch detection by a self-capacitive system(a self-detection system). Touch detection means that contact oradjacency of a detection object with or to a sensor electrode isdetected using the sensor electrode.

As shown in FIG. 1, touch detection by a self-capacitive system isperformed by supplying a sensor signal 101 to a sensor electrode 100 andreading change in the sensor signal (specifically, change in thecapacitance of the sensor signal). The sensor signal is changed inconnection with contact or adjacency of a detection object O which canbe regarded as a dielectric substance such as fingers or a stylus(hereinafter, simply referred to as a detection object) with or to thesensor electrode 100. The change in the sensor signal is detected by adetection circuit 102.

Touch detection by a self-capacitive system uses capacitance Cx1 of thesensor electrode and capacitance Cx2 produced by the detection object Oadjacent to the sensor electrode 100.

In FIG. 2, solid line A shows temporal change in the sensor signal whenthe detection object O is neither in contact with nor adjacent to thesensor electrode 100. Since the detection object O is not close to thesensor electrode 100, no capacitance is produced between the sensorelectrode SE and the detection object O. Only capacitance Cx1 of thesensor electrode is produced. The sensor signal 101 read by thedetection circuit 102 exhibits the temporal change shown by solid line Ain accordance with the input of the sensor signal 101 to the sensorelectrode 100.

When the detection object O approaches or makes in contact with thesensor electrode 100 from the above state, capacitance Cx2 is producedbetween the sensor electrode 100 and the detection object O. Bycapacitance Cx2, a large amount of current is supplied to the sensorelectrode SE. In FIG. 2, the dashed line shows change in the sensorsignal in accordance with the charge amount when the detection object Ois adjacent to the sensor electrode 100. As shown by the dashed line,the change is larger by charge amount ΔQ than that when the detectionobject O is not present. This difference is detected by the detectioncircuit 102, and thus, the state of adjacency of the detection object Ois determined.

First Embodiment

Now, this specification explains the details of a display device havinga touch function and a method of driving the display device according toa first embodiment with reference to the accompanying drawings.

As shown in FIG. 3, in the present embodiment, a display device 1 havinga touch function comprises a liquid crystal display panel 2 in an activematrix type, and a backlight unit (not shown) provided on the rear sideof the liquid crystal display panel 2. The display device 1 having atouch function displays an image with the light emitted from thebacklight unit such that the surface opposite to the rear surface onwhich the backlight unit is provided is a display surface 11.

Hereinafter, a state in which the display surface 11 is viewed in thenormal direction of the display surface 11 is called a plan view.

The liquid crystal display panel 2 comprises a first substrate 3, asecond substrate 4 facing the first substrate 3, and a liquid crystallayer (the liquid crystal layer 5 shown in FIG. 5 later) providedbetween the first substrate 3 and the second substrate 4. The secondsubstrate 4 faces the first substrate 3 on the display surface 11 side.

A rectangular display area 12 which allows the display surface 11 todisplay an image is provided on the liquid crystal display panel 2.Further, a frame-like non-display area 13 is provided around the displayarea 12 on the liquid crystal display panel 2.

The display area 12 may have a different shape such as a trapezoidalshape, a pentagonal shape, a hexagonal shape, an octagonal shape,another polygonal shape, a circular shape or an elliptical shape.Further, the liquid crystal display panel 2 may have a shape based onthe display area 12, such as a trapezoidal shape, a pentagonal shape, ahexagonal shape, an octagonal shape, another polygonal shape, a circularshape or an elliptical shape. The shape of the liquid crystal displaypanel 2 is not necessarily the same as that of the display area 12. Theymay have different shapes. In addition, the liquid crystal display panel2 may be deformed in an antiplane direction, and thus, may be a curvedpanel.

The liquid crystal display panel 2 has a touch detection function fordetecting a touch with the detection object O on the display surface 11.To realize a display function and a touch function, the display device 1having a touch function comprises a drive controller 40. The drivecontroller 40 comprises a display drive controller 50 which controlsdriving for displaying an image on the display surface 11, and a sensordrive controller 60 which controls driving for detecting a touch withthe detection object O on the display surface 11.

In the following description, a touch refers to either contact oradjacency of a detection object with or to the display surface 11. Themain part of the sensor drive controller 60 may be formed in, forexample, an integrated circuit (IC; a controller 54) into which thedrive controller 50 is incorporated. The sensor drive controller 60 maybe formed on the first substrate SUB1 as a separate circuit.

Alternatively, the sensor drive controller 60 may be formed on aflexible printed circuit (FPC) board as a circuit, or may be provided inanother IC connected via an FPC board. The sensor drive controller 60 ispartially formed in the display area and includes a switch drive circuit80.

Now, this specification explains the specific structure of the liquidcrystal display panel 2, mainly, the display area 12. The specificationfurther explains the specific structures of the display drive controller50 and the sensor drive controller 60.

The first substrate 3 comprises n first wirings (gate lines) 20 and msecond wirings (data lines) 21 at positions corresponding to the displayarea 12 on the inner surface of the first substrate 3. Further, on theinner surface of the first substrate 3, a plurality of pixel electrodes22 and a plurality of common electrodes 26 are formed. Note, above thewiring may be called an interconnection.

The gate lines 20 extend in a first direction X and are arranged atintervals in a second direction Y perpendicular to the first directionX.

The data lines 21 extend in the second direction Y and are arranged atintervals in the first direction X. By this structure, the data lines 21intersect with the gate lines 20 in a plan view.

The common electrodes 26 are arranged in matrix in the display area 12.Each common electrode 26 faces a plurality of pixel electrodes 22.

As described above, the gate lines 20 intersect with the data lines 21in a plan view. Thus, a plurality of pixel areas 27 defined by the gatelines 20 and the data lines 21 are formed in the display area 12. Thepixel areas 27 are arranged in matrix in the first and second directionsX and Y in the display area 12. In the display area 12, m×n pixel areas27 are formed, where m and n are positive integers.

The first direction X must intersect with the second direction Y. In theabove explanation, the first direction X is perpendicular to the seconddirection Y. However, the intersecting state includes a state other thana perpendicular state. For example, the first direction X may besubstantially perpendicular to the second direction Y.

As described above, the pixel areas 27 are arranged in matrix in thepresent embodiment. In consideration of this structure, the firstdirection X and the second direction Y are also called a row directionand a column direction, respectively, in the following explanation.

The gate lines 20 and the data lines 21 are linearly formed in thepresent embodiment. However, the gate lines 20 and the data lines 21 maybe curved partially or at a plurality of positions. For example, thegate lines 20 and the data lines 21 may be bent in each pixel area 27such that the lines have a wave shape.

As shown in FIG. 4, each pixel area 27 includes the pixel electrode 22,and a pixel switching element 28 which connects the pixel electrode 22and the data line 21. Each common electrode 26 is provided so as to facea plurality of pixel electrodes 22. In the present embodiment, forexample, 400 pixel electrodes (=20 pixel electrodes×20 pixel electrodes)face one common electrode 26. In the display area 12, a plurality ofcommon electrodes 26 are arranged in matrix.

The pixel switching element 28 is formed by a thin-film transistor(TFT). The gate electrode of the thin-film transistor is connected tothe gate line 20. The source electrode is connected to the data line 21.The drain electrode is connected to the pixel electrode 22.

FIG. 5 is a cross-sectional view schematically showing the layerstructure of the liquid crystal display panel 2. The cross-sectionalview of FIG. 5 is taken along dashed line X-X′ of FIG. 4. FIG. 5 showsthe cross-sectional surface of a pixel switch 28 a, the cross-sectionalsurface of a select switching element 81 a, and the cross-sectionalsurface of a pixel switch 28 b regarding FIG. 4.

As shown in FIG. 5, the first substrate 3 is attached to the secondsubstrate 4 via a sealing material (not shown) across a predeterminedintervening cell gap G. The sealing material is provided in arectangular form along the display area 12 in the non-display area 13.The liquid crystal layer 5 is encapsulated in the space surrounded bythe first substrate 3, the second substrate 4 and the sealing material.A plurality of spacers 7 which keep the cell gap G constant are providedbetween the pair of substrates 3 and 4.

The first substrate 3 is formed using a first insulating substrate 3 ahaving a phototransmissive property, such as a glass substrate or aresin substrate. A plurality of light-shielding layers 31 formed ofmetal are provided in an island form on a surface (inner surface) of thefirst insulating substrate 3 a so as to face the second substrate 4. InFIG. 5, the light-shielding layers 31 are shown as light-shieldinglayers corresponding to the pixel switching elements 28. Light-shieldinglayers 84 are shown as light-shielding layers corresponding to selectswitching elements 81 a and 81 b described later. In FIG. 5, the layerstructure of select switching element 81 a is shown. A first insulatinglayer 32 is formed so as to cover the inner surface of the firstinsulating substrate 3 a and the light-shielding layers 31.

A semiconductor layer 33, which is a channel layer, is formed at aposition corresponding to the light-shielding layers 31 on the firstinsulating layer 32. Further, on the first insulating layer 32, a gateinsulating film 34 is formed so as to cover the semiconductor layer 33.On the gate insulating layer 34, each gate line 20 is formed at aposition facing the semiconductor layer 33.

Over the inner surface of the first insulating substrate 3 a, further, asecond insulating layer 35 is provided so as to cover the gate lines 20and the gate insulating film 34. On the second insulating layer 35, aplurality of data lines 21 are formed. In the same layer as the datalines 21, a pair of electrode portions 36 (36 a and 36 b) is formed at aposition facing the semiconductor layer 33. The pair of electrodeportions 36 is in contact with the semiconductor layer 33 via the secondinsulating layer 35 and the gate insulating film 34. Each pixelswitching element 28 is formed by the gate lines 20, the semiconductorlayer 33 and the pair of electrode portions 36.

In the present embodiment, a top-gate TFT is employed as each pixelswitching element 28. However, a bottom-gate TFT may be employed. Inother words, the lower position of the semiconductor layer 33 and theupper positions of the gate lines 20 may be reversed. In addition, thesemiconductor layer 33 of each pixel switching element 28 is formed oflow-temperature polysilicon. However, the semiconductor layer 33 may beformed of amorphous silicon.

A planarization film 37 is provided so as to cover the data lines 21,the pair of electrode portions 36 and the second insulating layer 35. Onthe planarization film 37, a third insulating layer 38 is provided. Onthe third insulating layer 38, the common electrodes 26 are provided.

As shown in FIG. 3 to FIG. 5, each common electrode 26 has a rectangularshape having a size which is allowed to face a plurality of pixel areas27 (for example, 20 pixel electrodes×20 pixel electrodes) in the displayarea 12. The common electrodes 26 are arranged in matrix in the firstdirection X and the second direction Y.

In the present embodiment, as described above, a plurality of commonelectrodes 26 are arranged in matrix. Thus, the common electrodes 26 arealso used as sensor electrodes for touch detection. The specificstructure as sensor electrodes is explained later.

A fourth insulating layer 39 is formed so as to cover the commonelectrodes 26 provided in a tile form, and the third insulating layer38. On the fourth insulating layer 39, each pixel electrode 22 isformed.

Every pixel area 27 comprises a pixel electrode 22. The pixel electrode22 faces the common electrode 26 via the fourth insulating layer 39. Thepixel electrode 22 has a comb shape such that a slit 24 and a lineportion 25 are alternately provided. The pixel electrode 22 is incontact with the electrode portion 36 of the pixel switching element 28via the third insulating layer 38.

Each common electrode 26 and each pixel electrode 22 are formed of atransparent conductive material such as ITO or IZO. The insulatinglayers 32, 35, 38 and 39, the gate insulating film 34 and theplanarization film 37 are formed of, for example, an organic insulatingmaterial such as polyimide resin, or an inorganic insulating materialsuch as silicon nitride or silicon oxide.

A first alignment film (not shown) which defines the initial alignmentof the liquid crystal molecules of the liquid crystal layer 5 isprovided so as to cover the pixel electrodes 22 and the fourthinsulating layer 39.

The second substrate 4 is formed using a second insulating substrate 4 ahaving a phototransmissive property, such as a glass substrate or aresin substrate. The second insulating substrate 4 a comprises, forexample, a black matrix 8 provided at a position facing the gate lines20 and the data lines 21, a color filter 10, an overcoat layer and asecond alignment film AL2 (none of them is shown) on a side facing thefirst substrate 3.

In the above pixel structure, an electric field is produced between thepixel electrodes 22 and the common electrodes 26. Thus, a fringeelectric field is produced between the pixel electrodes 22 and thecommon electrodes 26 via the slits 24 of the pixel electrodes 22. By thefringe electric field, the orientation of the alignment of the liquidcrystal molecules of the liquid crystal layer 5 is changed. In this way,the optical characteristics of the liquid crystal layer 5 vary dependingon the pixel area 27. As a result, it is possible to display an image onthe display surface 11. The display mode using a fringe electric fieldis called a fringe field switching (FFS) mode.

As shown in FIG. 3, the first substrate 3 comprises a gate line drivecircuit 51 which drives the gate lines 20, a multiplexer 53 whichcontrols an image signal transmitted to the data lines 21, and the maincontroller 54 which controls the gate line drive circuit 51 and themultiplexer 53. Out of these circuits, the gate line drive circuit 51and the multiplexer 53 are formed on the first substrate 3. The maincontroller 54 is formed as an IC chip, and is mounted on the firstsubstrate 3. The gate line drive circuit 51 and the multiplexer 53 areelectrically connected to the main controller 54 via control lines 56 aand 56 b.

As shown in FIG. 6A, the main controller 54 comprises a data line drivecircuit 55 for driving the data lines 21 via the multiplexer 53. Themain controller 54 further comprises a timing controller (a controller)57 for controlling the data line drive circuit 55, the gate line drivecircuit 51 and the multiplexer 53. FIG. 6A mainly shows the structuralelements which contribute to display such that the structures of thepresent embodiment can be easily understood. FIG. 6B mainly shows thestructural elements which contribute to touch detection. In the actualdevice, the structural elements shown in FIG. 6A and FIG. 6B areintegrally formed.

As shown in FIG. 6A, the gate lines 20 formed in the display area 12extend to the non-display area 13, and are connected to the gate linedrive circuit 51. The gate line drive circuit 51 comprises a pluralityof gate shift registers 52 electrically connected to each other. Thegate lines 20 are connected to the gate shift registers 52 in aone-to-one relationship. In FIG. 6A, the gate line drive circuit 51 isprovided on each side of the display area 12 in a horizontal direction(direction X). However, the gate line drive circuit 51 may be providedonly one of the two sides.

The data lines 21 extend to the outside of the display area 12, and areconnected to the multiplexer 53. In FIG. 6A, third wirings 77 a and 77 bused for touch detection are shown. Third wirings 77 a and 77 b areformed at positions overlapping the data lines 21, which are secondwirings, via the insulating layer.

As shown in FIG. 3, a flexible wiring 58 is provided at a positionfacing the main controller 54 on the first substrate 3. The flexiblewiring 58 connects an external control module (not shown) such as anexternal application processor to the main controller 54.

In the present embodiment, a sensor drive controller 60 for detecting atouch with the detection object O on the display surface 11 is furtherformed on the liquid crystal display panel 2. More specifically, astructure for using the common electrodes 26 which contribute to displayas sensor electrodes SE and driving the common electrodes 26 so as tofunction as sensor electrodes SE is formed in the display area 12 andthe non-display area 13.

As shown in FIG. 3, FIG. 6A, FIG. 6B and FIG. 7A, the sensor drivecontroller 60 causes the common electrodes 26 to function as sensorelectrodes SE. The sensor drive controller 60 comprises a sensingcircuit 61 which detects presence or absence of a touch based on asensor signal, and a select circuit 62 which selects one of the commonelectrodes 26 as a sensor electrode SE. The main controller 54 comprisesa common electrode drive circuit 73 for supplying a signal to the commonelectrodes 26 separately from the sensing circuit 61.

FIG. 7A shows the select circuit 62 for causing the common electrode 26to operate as a sensor electrode SE. FIG. 7A shows one of the sensorelectrodes SE (common electrodes 26) of FIG. 6B as a representativeexample. The select circuit 62 comprises a pair of third wirings 77 aand 77 b provided so as to face the common electrode 26, the switchportions 81 including select switching elements 81 a and 81 b connectingthird wirings 77 a and 77 b to the common electrode 26, and switch lines79 a and 79 b connected to the switch portions 81. Switch lines 79 a and79 b are connected to the switch drive circuit 80 in the non-displayarea 13. The switch portions 81 are formed for each common electrode 26.

As shown in FIG. 4 and FIG. 6B, in the display area 12, a plurality ofthird wirings 77 including a pair of third wirings 77 a and 77 b extendin the second direction Y, which is the extension direction of the datalines 21. The third wirings 77 are provided at predetermined intervalsin the first direction X. In the present embodiment, the third wirings77 are provided at positions which overlap or substantially overlap thedata lines 21 via the insulating layer in a plan view. The third wirings77 are formed on the planarization film 37 and are covered by the thirdinsulating layer 38 together with the planarization film 37 such thatthe third wirings 77 overlap the data lines 21 (see FIG. 5).

The number of third wirings 77 may be any number as long as at least onepair of third wirings 77 a and 77 b is provided for each commonelectrode 26. For example, the third wirings 77 may overlap all the datalines 21 such that each common electrode 26 faces the same number ofthird wirings 77 (77 a and 77 b) as the number of data lines 21. In thiscase, the third wirings 77 may be used as dummy wirings.

The switch portions 81 include a pair of select switching elements 81 aand 81 b formed between a pair of third wirings 77 a and 77 b and thecommon electrode 26. Select switching elements 81 a and 81 b may be setto an on-state or off-state by control voltage from switch lines 79 aand 79 b, respectively. In the pixel area 27 in which each of selectswitching elements 81 a and 81 b is provided, the area of the pixelelectrode 22 is reduced by the area of the select switching element.More specifically, the line portions 25 corresponding to each of selectswitching elements 81 a and 81 b are shortened. In the space generatedby this structure, each of select switching elements 81 a and 81 b isformed.

In the pixel area 27 in which each of select switching elements 81 a and81 b is provided, the opening rate subjected to display is reduced bythe area of the select switching element. In terms of this factor, asthe pixel in which each of select switching elements 81 a and 81 b isprovided, the pixel area 27 corresponding to blue (B) is desirable.

As shown in FIG. 5, each select switching element (select switchingelement 81 a is shown in FIG. 5 as a representative example) is formedby a thin-film transistor (TFT) having a structure similar to that ofeach pixel switching element 28 which connects the pixel electrode 22and the data line 21.

Specifically, select switching element 81 a comprises a semiconductorlayer 82 formed in the same layer as the semiconductor layer 33 of thepixel switching element 28, and a pair of electrode portions 83 a and 83b in the same layer as the pair of electrode portions 36 a and 36 b ofthe pixel switching element 28. The pair of electrode portions 83 a and83 b is in contact with the semiconductor layer 82 via the gateinsulating film 34. The light-shielding layer 84 is provided at aposition facing the semiconductor layer 82 of select switching element81 a. The light-shielding layer 84 is formed in the same layer as thelight-shielding layer 31 of the pixel switching element 28.

In the present embodiment, the light-shielding layer 84, thesemiconductor layer 82 and the pair of electrode portions 83 a and 83 bin each select switching element 81 are formed in the same layers as thestructures of each pixel switching element 28. In this way, each ofselect switching elements 81 a and 81 b can be formed in the steps forforming each pixel switching element 28. Thus, it is possible to preventincrease in the number of steps caused by forming each select switchingelement 81 a or 81 b. However, each structure of each select switchingelement 81 a or 81 b may be formed in a layer or way different fromthose of each pixel switching element 28.

Regarding select switching element 81 a, third wiring 77 a is in contactwith electrode portion 83 a on the source side via the planarizationfilm 37. The common electrode 26 is in contact with electrode portion 83b on the drain side via the third insulating layer 38 and theplanarization film 37. In this way, select switching element 81 aconnected to the common electrode 26 is formed. Select switching element81 b is also formed in the same process as that of select switchingelement 81 a. Select switching element 81 a is connected to third wiring77 a, and select switching element 81 b is connected to third wiring 77b. Select switching element 81 a is controlled so as to be in anon-state or off-state by control voltage from switch line 79 a. Selectswitching element 81 b is controlled so as to be in an on-state oroff-state by control voltage from switch line 79 b.

Both select switching element 81 a and select switching element 81 b areformed as, for example, n-TFT. The semiconductor channel is not limitedto this example. Select switching elements 81 a and 81 b may be formedas p-TFT. When they are formed with the same channel, the manufacturingconvenience is improved.

Switch lines 79 a and 79 b are formed in the same layer as the gatelines 20, and are covered by the second insulating layer 35 in the samemanner as the gate lines 20 (switch line 79 a is shown in FIG. 4 andFIG. 5, and switch lines 79 a and 79 b are shown in FIG. 6A).

As shown in FIG. 3, FIG. 4 and FIG. 6B, switch lines 79 a and 79 bextend in the first direction X, which is the extension direction ofeach gate line 20. Switch lines 79 a and 79 b are provided atpredetermined intervals in the second direction Y. More specifically, apair of switch lines 79 a and 79 b is provided for a plurality of commonelectrodes 26 arranged in a corresponding row.

With the above structure, the switch portions 81 switch the state ofconnection between the third wirings 77 and the common electrodes 26 asfollows.

When a switch signal is input to switch line 79 a, select switchingelement 81 a is set to an on-state in response to the signal, and thecommon electrode 26 is connected to third wiring 77 a. In a state wherea switch signal is not supplied to switch line 79 a, select switchingelement 81 a is set to an off-state, and the common electrode 26 isdisconnected from third wiring 77 a. When a switch signal is input toswitch line 79 b, select switching element 81 b is set to an on-state,and the common electrode 26 is connected to third wiring 77 b. In astate where a switch signal is not supplied to switch line 79 b, selectswitching element 81 b is set to an off-state, and the common electrode26 is disconnected from third wiring 77 b.

When one common electrode 26 is connected to third wiring 77 a or 77 b,this state is indicated as ON. When they are disconnected from eachother, the state is indicated as OFF. In this case, it is possible toobtain a sensing state, a guard state and a floating state as followsbased on the presence or absence of a switch signal from switch lines 79a and 79 b.

<Sensing State>

A switch signal from switch line 79 a is present, and select switchingelement 81 a is ON.

A switch signal from switch line 79 b is absent, and select switchingelement 81 b is OFF.

When a switch signal is present, for example, the signal is high. When aswitch signal is absent, for example, the signal is low.

A common electrode 26 in a sensing state may be called a sensing(sensor) electrode.

<Guard State>

A switch signal from switch line 79 a is absent, and select switchingelement 81 a is OFF.

A switch signal from switch line 79 b is present, and select switchingelement 81 b is ON.

A common electrode 26 in a guard state may be called a non-sensingelectrode or a guard electrode.

<Floating State>

A switch signal from switch line 79 a is absent, and select switchingelement 81 a is OFF.

A switch signal from switch line 79 b is absent, and select switchingelement 81 b is OFF.

A common electrode 26 in a floating state may be called a non-sensingelectrode or a floating electrode.

Each row of common electrodes 26 shown in FIG. 6B is set to the sameswitching state in accordance with the combination of presence andabsence of a switch signal from switch lines 79 a and 79 b as explainedabove.

FIG. 6B shows an example of a period of touch detection. In touchdetection, the common electrodes 26 which belong to a predetermined roware selected as the sensor electrodes 26 (SE). When the predeterminedrow is row 26AL, row 26AL is set to a sensing state.

The upper and lower rows adjacent to row 26AL are controlled so as to bein a guard state. A pair of rows 26GL adjacent to row 26AL of sensorelectrodes in a sensing state is set to a guard state. Thus, it ispossible to prevent the electric field generated in the sensorelectrodes 26 (SE) from spreading off the upper side of the sensorelectrodes.

Each row 26FL is a row which is away from the row of common electrodes26 selected as the sensor electrodes 26 (SE) across at least oneintervening row. Each row 26FL is set to a floating state. No signal isinput to the rows in a floating state. Thus, power consumption isreduced in comparison with that when a guard signal is input. In FIG.6B, one row is selected as the row of common electrodes 26 (SE) in asensing state, and only the rows immediately above and under theselected row are in a guard state. However, a plurality of rows may beset to a guard state on each of the upper and lower sides.

In addition to the sensing circuit 61 and the select circuit 62, thesensor drive controller 60 comprises the switch line drive circuit 80and the common electrode drive circuit 73. The switch line drive circuit80 is formed along the gate line drive circuit 51 in the non-displayarea 13. The common electrode drive circuit 73 and the sensing circuit61 are incorporated into the IC chip which is the main controller 54.

The switch line drive circuit 80 is connected to the main controller 54via a control line 86. The switch lines 79 extend to the non-displayarea 13, and are connected to the switch line drive circuit 80.

As shown in FIG. 6B, a pair of third wirings 77 a and 77 b extends tothe main controller 54, and is connected to the common electrode drivecircuit 73 and the sensing circuit 61 in the main controller 54.

As shown in FIG. 7A, the common electrode drive circuit 73 includes aguard signal line GSL and a common voltage line CVL. The guard signalline GSL is connected to a guard signal generation module 75. The guardsignal line GSL can be connected to third wiring 77 b via a guard signalswitch GSW. The guard signal switch GSW is controlled so as to be in anon-state or off-state by a switch control signal xSW1 from the timingcontroller 57. The common voltage line CVL is connected to aconstant-voltage circuit formed in the main controller 54, for example,a common voltage generation module 74. The common voltage line CVL canbe connected to third wiring 77 b via a common voltage switch CSW in thedisplay period (Display) shown in FIG. 8.

Now, this specification explains a circuit operation for obtaining theoperation state of the common electrode 26 in a display period and theoperation state in a touch period in FIG. 7A.

(a) Common Electrode 26 in Display Period

In this period, select switching element 81 b is set to an on-state by aswitch signal from switch line 79 b, and select switching element 81 ais set to an off-state by a switch signal from switch line 79 a. SwitchCSW is set to an on-state by a switch control signal SW1 from the timingcontroller 57. As a result, the common voltage from the common voltagegeneration module 74 is applied to the common electrode 26 in a displayperiod.

(b) Common Electrode 26 in Touch Period

In this period, the common electrode 26 may be set to one of thefollowing three states based on the position of touch scanning. Thethree states are a sensing state, a guard state and a floating state.

(b-1) Set to Sensing State

In this case, select switching element 81 b is set to an off-state by aswitch signal from switch line 79 b, and select switching element 81 ais set to an on-state by a switch signal from switch line 79 a. Thus, asensing signal having a predetermined pulse wave is supplied from thesensing circuit 61 to the common electrode 26 via third wiring 77 a. Atthis time, the sensing circuit 61 detects whether or not a detectionobject is in contact with the common electrode 26. The sensing circuit61 is explained in detail later.

(b-2) Set to Guard State

In this case, select switching element 81 b is set to an on-state by aswitch signal, and select switching element 81 a is set to an off-stateby a switch signal. Switch GSW is set to an on-state by a switch controlsignal xSW1 from the timing controller 57. Switch CSW is set to anoff-state. As a result, a guard signal is supplied from the guard signalgeneration module 75 to the common electrode 26.

(b-3) Set to Floating State

In this case, select switching element 81 b is set to an off-state by aswitch signal, and select switching element 81 a is set to an off-stateby a switch signal. As a result, no signal is supplied to the commonelectrode 26. No voltage is applied to the common electrode 26. Thus,the common electrode 26 is set to a floating state.

The above sensing circuit 61 is further explained. The sensing circuit61 is a circuit for realizing touch detection by a self-capacitivesystem, and comprises a sensor signal generation module 64, a mirrorcircuit 65 and a detection circuit 66. The sensor signal generationmodule 64 generates a predetermined pulse wave as a sensor signal. Thepulse wave has the same waveform and the same phase as those of thepulse wave of the guard signal generation module 75.

The mirror circuit (current mirror circuit) 65 is connected to thesensor signal generation module 64 on the upstream side, and isconnected to third wiring 77 a on the downstream side. The mirrorcircuit 65 is connected to the detection circuit 66. The mirror circuit65 has this state of connection. Thus, when a sensor signal is suppliedfrom the sensor signal generation module 64 to third wiring 77 a, thesame signal as the sensor signal is input to the detection circuit 66 asit is.

The detection circuit 66 comprises a switch 70 a, a comparison device67, an A/D converter 68 and a filter 69.

The comparison device 67 receives a sensor signal via the mirror circuit65. The connection between the comparison device 67 and the commonelectrode 26 selected as a sensor electrode SE is switched by switch 70a provided in the former stage of the comparison device 67. A capacitor67 and a switch 70 b are connected to the comparison device 67 inparallel. The output of the comparison device 67 is reset by switchingswitch 70 b. The timing controller 57 controls switching switch 70 a andswitch 70 b.

The A/D converter 68 converts the value output by the comparison device67 into a digital signal, and outputs it to an external processingcircuit (not shown). A calculation process is performed in theprocessing circuit based on the data from each detection circuit 66. Inthis way, the position of a touch is specified. The principle of touchdetection is explained above with reference to FIG. 1 and FIG. 2.

As described above, the detection circuit 66 of the sensing circuit 61is provided for each select circuit 62. More specifically, one detectioncircuit 66 is provided for the common electrodes (or the group of commonelectrodes) 26 in one column connected to a pair of third wirings 77 aand 77 b. Thus, at least one detection circuit 66 must be provided foreach column of common electrodes 26. The number of detection circuits 66is extremely less than that of common electrodes 26.

The display device of the present embodiment has the above structures.Thus, it is possible to decrease the area of the sensing circuit(detection circuit) 61 or an IC including the sensing circuit (detectioncircuit) 61. In addition, the display device is advantageous in terms ofpower saving and manufacturing.

FIG. 7B shows an example of relationships between sensor signal voltage,guard signal voltage and floating voltage as described above. Theamplitude (voltage)±of a sensor signal based on reference voltage Vf(Vf±Vdet1) may be the same as that of a guard signal based on referencevoltage Vf (Vf±Vg). However, the amplitude of a guard signal ispreferably less than that of a sensor signal. For example, the voltageof a guard signal is set between floating voltage Vf and the maximumvoltage of a sensor signal (for example, set to half of the difference).This adjustment is performed by the output voltage adjustment of theguard signal generation module 75 and the output voltage adjustment ofthe sensor signal generation module 64.

In the above manner, the drive controller 40 sets the phase of an ACsensing signal supplied to a sensor electrode so as to be the same asthat of an AC guard signal supplied to a guard electrode. The drivecontroller 40 sets the amplitude (voltage) of an AC guard signal so asto be less than that of an AC sensing signal. In other words, the drivecontroller 40 sets the amplitude (voltage) of an AC guard signal so asto be close to floating voltage. In this way, it is possible to reducepower consumption in each row supplied with a guard signal. Incomparison with a case where a guard signal has the same amplitude as asensing signal, it is possible to reduce the difference in potentialbetween a floating electrode and a sensor electrode in a touch period.This specification further explains a method of driving the displaydevice 1 having a touch function with reference to FIG. 6A, FIG. 6B,FIG. 7A, FIG. 7B and FIG. 8.

As shown in FIG. 8, in the present embodiment, the display device 1having a touch function is controlled by the drive controller 40. Bythis control, a display period (Display) for displaying an image on thedisplay surface 11 and a sensor period (Touch) for detecting a touch onthe display surface 11 are alternately provided. This control isperformed in series based on a clock signal from the timing controller57.

In each display period (Display), a switch signal for setting all ofselect switching elements 81 b to an on-state and setting all of selectswitching elements 81 a to an off-state is output from the switch drivecircuit 80. Switches CSW provided in the common electrode drive circuit73 in FIG. 7A are set to an on-state. Thus, all of the common electrodes26 are maintained at certain common voltage (VCOM).

Further, in the display period (Display), a signal is input to the gateshift registers 52 (see FIG. 6A) in a time-divisional manner. Thus, agate signal is supplied to the pixel switching elements 28 in thedisplay area 12 via the gate lines 20. Thus, the pixel switchingelements 28 are set to an on-state. At this time, an image signal issupplied to the pixel electrodes 22 in an on-state via the data linedrive circuit 55 and the multiplexer 53. As a result, the image signalis written to the pixel electrodes 22.

Thus, a fringe electric field is generated between the common electrodes26 and the pixel electrodes 22 in an on-state. The optical property ofthe liquid crystal layer 5 is changed by the fringe electric field. Inthis way, an image is displayed in the pixel areas 27.

In the display period, the gate shift registers 52 vertically adjacentto each other are operated in order from the upper side. Thus, the pixelareas 27 in several tens to several hundreds of rows are scanned in aline-sequential system. In this way, an image is displayed in series.

After the display period (Display) ends, a sensor period (Touch) starts.In the sensor period (Touch) for detecting a touch, each row of commonelectrodes 26 is controlled so as to be in a sensing state forperforming touch detection in series. FIG. 8 shows how the state ofselect switching elements 81 b and 81 a controlled by switch lines 79 band 79 a is changed between ON and OFF when the N^(th) row, the N+1^(th)row, the N+2^(th) row, the N+3^(th) row, . . . , are controlled so as tobe in a sensing state in series.

When the N+1^(th) row is controlled so as to be in a sensing state (seeperiod t11 shown in FIG. 8), select switching elements 81 a are set toan on-sate based on a switch signal (for example, a high switch signal)from switch line 79 a, and select switching elements 81 b are set to anoff-state based on a switch signal (for example, a low switch signal)from switch line 79 b. In this manner, the common electrodes 26 in theN+1^(th) row are set as the sensor electrodes SE, and are supplied witha pulse signal from the pulse signal generation module 64 via the mirrorcircuit 65. At this time, the same signal as the pulse signal is inputto the detection circuit 66 via the mirror circuit 65.

When a detection object O touches the display surface 11 facing thesensor electrodes SE, the pulse signal from the sensor signal generationmodule 64 is changed by the effect of the detection object O. The changein the pulse signal is input to the comparison device 67 of thedetection circuit 66, is converted into digital data by the A/Dconverter 68, and is transmitted to the subsequent processing circuits.

In the sensor period (Touch), a pulse signal is supplied from the mirrorcircuit 65 to each third wiring 77 a. In the rows other than the row ofcommon electrodes 26 selected as the sensor electrodes SE (in otherwords, in the non-sensing rows), all of select switching elements 81 aare set to an off-state (see the the N^(th) row, the N+2^(th) row andthe N+3^(th) row in FIG. 8). Thus, no pulse signal for sensing issupplied to the non-sensing rows.

The guard signal switches GSW are set to an on-state. Thus, a guardsignal is supplied to third wirings 77 b via the guard signal line GSLand the guard signal switches GSW. However, a guard signal is notsupplied to the common electrodes 26 currently set to a sensing statesince select switching elements 81 b connected to the common electrodes26 in a sensing state are set to an off-state. In the common electrodes26 in the upper and lower non-sensing rows adjacent to the row of commonelectrodes 26 in a sensing state, select switching elements 81 b are setto an on-state. Thus, a guard signal is supplied to the commonelectrodes 26 in the upper and lower non-sensing rows. Further, all ofselect switching elements 81 b connected to the common electrodes 26 inthe other non-sensing rows are set to an off-state. Thus, the commonelectrodes 26 in the other non-sensing rows are set to a floating state.In this way, power consumption is reduced in the rows in a floatingstate in comparison with the rows in a guard state.

As described above, while touch detection is performed by the sensorelectrodes SE (common electrodes 26) in the sensing row, a guard signalis input from the guard signal generation module 75 to the commonelectrodes 26 in at least a pair of upper and lower non-sensing rowsadjacent to the sensing row.

The guard signal is a pulse signal having the same waveform as that ofthe pulse signal generated by the sensor signal generation module 64.

Thus, the same signal as the sensor signal of the sensing circuit 61 issupplied to the common electrodes 26 in the above pair of non-sensingrows in a state where the common electrodes 26 are not connected to thesensing circuit 61. In this manner, generation of unnecessarycapacitance is prevented as much as possible between the sensorelectrodes SE and the common electrodes 26 in the pair of non-sensingrows. As described above, a guard signal may have a phase which issubstantially the same as that of the pulse signal generated by thesensor signal generation module 64, and may have an amplitude slightlyless than that of the pulse signal.

Touch detection by a self-capacitive system is performed by detectingchange in the charge in connection with change in the capacitance of thesensor electrodes SE. The change in capacitance includes change incapacitance between the detection object O and the sensor electrodes SEnecessary for touch detection as well as change in capacitance betweenthe sensor electrodes SE and the other electrodes around the sensorelectrodes SE unnecessary for touch detection. To solve this problem, asdescribed above, a guard signal is input to the common electrodes 26other than the sensor electrodes SE. Thus, generation of unnecessarychange in capacitance can be prevented as much as possible. Further, itis possible to reduce the proportion of unnecessary change incapacitance in change in capacitance for touch detection. In this way,the detection circuit 66 is capable of receiving change in thecapacitance of the sensor electrodes SE in a state where the proportionof change in capacitance caused by the detection object is increased. Asa result, detection accuracy can be further improved.

The same pulse wave is written to sensor electrodes SE and the commonelectrodes 26 in the upper and lower non-sensing rows adjacent to thesensor electrodes SE at the same time. Thus, lines with equal electricforce are formed from all the common electrodes 26 toward the upperside.

In general, lines of electric force have repulsion each other. In thepresent embodiment, it is possible to exert the effect of lines ofelectric force from the sensor electrodes SE on the upper side incomparison with when the guard signal having the same waveform as thatof the sensor signal is not output by the common electrodes 26 aroundthe sensor electrodes SE. In this manner, it is possible to detect adetection object O relatively far from the display surface 11. As aresult, even when the sensor electrodes SE are apart from the detectionobject O by providing a glass cover, etc., over the liquid crystaldisplay panel 2, detection accuracy is sufficiently maintained. Evenwhen the sensor electrodes SE are provided on a deep side (on thebacklight side) relative to the display surface 11, detection accuracyis sufficiently maintained. It is possible to detect a detection objectO even when the detection object O is apart from the sensor electrodesSE such that the detection object O is not directly in contact with thesensor electrodes SE.

In the present embodiment, the display device 1 having a touch functioncomprises the select circuit 62 such that the specific common electrodes26 are selected as sensor electrodes SE in each sensor period, and thesensor electrodes SE are connected to the sensing circuit 61. Thus,there is no need to provide the same number of detection circuits 66 asthe number of common electrodes 26. The number of detection circuits 66may be less than the number of common electrodes 26. As a result, it ispossible to flexibly deal with increase in the number of commonelectrodes 26 in connection with realization of high-accuracy touchdetection or with increase in the size of the display area 12. Moreover,it is possible to flexibly respond to reduction in the size of frame, inother words, reduction in the width of the non-display area 13.

Switch portions 78 which switch the state of connection between thecommon electrodes 26 and the sensing circuit 61 are provided in thedisplay area 12. In this manner, it is possible to prevent expansion ofthe non-display area 13 caused by the presence of the switch portions78. Since the switch portions 78 are formed in the normal steps forforming the display area 12, it is possible to prevent increase in thenumber of manufacturing steps in connection with formation of the switchportions 78.

FIG. 9 is shown for explaining a structural example and an operation ofthe switch line drive circuit 80 used in the display device 1 of thefirst embodiment. The switch line drive circuit 80 comprises switchesswb and swa for outputting a switch signal to switch lines 79 b and 79a, respectively.

Switches swb and swa are capable of selecting a switch signal of logic“1” or logic “0” and outputting it in accordance with a control signalalternately supplied based on the touch period. In accordance with theswitch signal, select switching elements 81 b and 81 a connected to eachcommon electrode 26 are controlled so as to be in an on-state oroff-state in each touch period.

The operation state of each common electrode 26 is set to a sensingstate or a non-sensing state (including a guard state and a floatingstate) based on the state of select switching elements 81 b and 81 a andthe state of the guard signal switch GSW explained earlier in a touchperiod (Touch). Each common electrode in which select switching elements81 b and 81 a are shown as OFF and ON, respectively, is in a sensingstate. Each common electrode in which select switching elements 81 b and81 a are shown as ON and OFF, respectively, is in a guard state. Eachcommon electrode in which select switching elements 81 b and 81 a areshown as OFF and OFF, respectively, is in a floating state.

In order to make the description clearer, FIG. 9 shows six rows eachincluding a plurality of common electrodes and assumes the six rows asone frame. FIG. 9 shows that the state of the common electrodes 26 ineach row is changed among three states, specifically, a sensing state, aguard state and a floating state, based on the touch period (Touch) astime passes. To realize this change, switches swb and swa select aswitch signal of logic “1” or a switch signal of logic “0” in each touchperiod in accordance with a control signal from register 801 or 802.When a first control signal is output from register 801 in a first touchperiod (Touch), a second control signal necessary for the next secondtouch period (Touch) is prepared in register 802. When the secondcontrol signal is output from register 802 in the second touch period(Touch), a third control signal necessary for the next third touchperiod (Touch) is prepared in register 801. In this manner, the sensingrow is changed (scanned) in order.

Second Embodiment

FIG. 10 shows a second embodiment. The same elements as those of FIG. 6Bare denoted by the same reference numbers. In the present embodiment,third wirings 77 b and switch lines 79 b are deleted from the embodimentshown in FIG. 6B. Each third wiring 77 a is connectable to a commonvoltage line CVL via a common voltage switch CSW. This connection iscontrolled so as to be off or on by a switch control signal SW1 from atiming controller 57. Each third wiring 77 a is connectable to a sensingcircuit 61 via a drive switch DSW. The drive switch DSW is controlled soas to be in an off-state or on-state by a switch control signal xSW1from the timing controller 57.

FIG. 11 is a timing chart shown for explaining the operation of theembodiment of FIG. 10. In the present embodiment, each third wiring 77 ais connected to the common voltage line CVL via the common voltageswitch SCW in a display period (Display). Thus, each sensor electrode SEfunctions as a common electrode 26 and contributes to display in adisplay period (Display). In a touch period (Touch), each third wiring77 a is connected to the sensing circuit 61 via the drive switch DSW.Only a switch signal from switch line 79 a in a predetermined row (inthe example of FIG. 10, sensing row 26AL) is, for example, high. Thus,corresponding switching elements 81 a are set to an on-state, and thesensor electrodes SE in row 26AL are set to a sensing state. At thistime, a switch signal from switch lines 79 a in the other rows(non-sensing rows) is low. Thus, corresponding switching elements 81 aare set to an off-state, and all of corresponding sensor electrodes SEare set to a floating state.

FIG. 12 is shown for explaining a structural example and an operation ofa switch line drive circuit 80 used in a display device 1 according tothe second embodiment. Switch swa is capable of selecting a switchsignal of logic “1” or logic “0” and outputting it in accordance with,for example, a control signal alternately supplied based on the frameperiod from registers 801 and 802. In accordance with the switch signal,select switching elements 81 a and 81 b connected to each commonelectrode 26 are controlled so as to be in an on-state or off-state ineach touch period.

The operation state of each common electrode 26 is set to a sensingstate or a floating state by the state of switch 81 a and the driveswitch DSW explained in FIG. 9 in a touch period (Touch).

In order to make the description clearer, FIG. 12 shows six rows eachincluding a plurality of common electrodes and assumes the six rows asone frame. FIG. 12 shows that the state of the common electrodes 26 ineach row is changed between a sensing state and a floating state basedon the touch period (Touch) as time passes. To realize this change,switch swa selects a switch signal of logic “1” or a switch signal oflogic “0” in each touch period in accordance with a control signal fromregister 801 or 802. When a first control signal is output from register801 in a first touch period (Touch), a second control signal necessaryfor the next second touch period (Touch) is prepared in register 802.When the second control signal is output from register 802 in the secondtouch period (Touch), a third control signal necessary for the nextthird touch period (Touch) is prepared in register 801. In this manner,the sensing row is changed (scanned) in order.

In the above embodiment, the common electrodes 26 in the rows excludingthe sensing row in a sensing state are set to a floating state. Thus, itis possible to prevent generation of capacitance between the sensorelectrodes SE in the sensing row and the common electrodes 26 in theupper and lower non-sensing rows adjacent to the sensor electrodes SE incomparison with a case where the common electrodes 26 in the non-sensingrows are always maintained at constant voltage. In the presentembodiment, only switching elements 81 a in the sensing row are set toan on-state, and all of switching elements 81 a in the other non-sensingrows are set to an off-state. Thus, power consumption can be reduced. Inaddition, since a guard signal is not used, power consumption can bereduced in comparison with the previous embodiment. In the secondembodiment, switch lines 79 b are unnecessary. The number of pixel areashaving a less opening rate can be decreased.

Third Embodiment

FIG. 13 is a plan view schematically showing a part of a liquid crystaldisplay device 1 having a touch function according to a thirdembodiment. The display device 1 having a touch detection function isdifferent from that of the first embodiment in terms of the structure ofconnection between switch lines 79 a and 79 b and each common electrode26, a switch line drive circuit 80, etc. However, the other structuresare the same as those of the first embodiment (FIG. 6B). Thus, the samestructures as those of the first embodiment are denoted by the samereference numbers, descriptions thereof being omitted.

As show in FIG. 13, in the present embodiment, a pair of switch lines 79a adjacent to each other in a second direction Y is connected to eachother. A pair of switch lines 79 b adjacent to each other in the seconddirection Y is also connected to each other. More specifically, an endportion of switch line 79 a extends from the switch line drive circuit80 to a non-display area 13 via a first row in a display area, andreturns to the display area on the switch line drive circuit 80 side viaa second row in the display area. Each switch line is connected to theswitch portions provided in the common electrodes.

In the present embodiment, in each sensor period, the common electrodes26 in two rows connected to each other can be collectively selected assensor electrodes SE. Thus, the total sensor period can be reduced byhalf.

In the present embodiment, a structure of connecting two switch lines 79adjacent to each other is employed. However, a structure of connectingthree or more switch lines 79 may be employed.

Fourth Embodiment

FIG. 14 is a plan view schematically showing a part of a liquid crystaldisplay device 1 having a touch function according to a fourthembodiment. The display device 1 having a touch detection function isdifferent from that of the first embodiment in terms of the structure ofconnection between switch lines 79 a and common electrodes 26, a switchline drive circuit 80, etc. However, the other structures are the sameas those of the second embodiment (FIG. 10). Thus, the same structuresas those of the second embodiment are denoted by the same referencenumbers, descriptions thereof being omitted.

As shown in FIG. 14, in the present embodiment, a pair of switch lines79 a adjacent to each other in a second direction Y is connected to eachother. More specifically, an end portion of switch line 79 a extendsfrom the switch line drive circuit 80 to a non-display area 13 via afirst row in a display area, and returns to the display area on theswitch line drive circuit 80 side via a second row in the display area.Each switch line is connected to switch portions 81 a provided in thecommon electrodes.

In the present embodiment, similarly, in each sensor period, the commonelectrodes 26 in two rows connected to each other can be collectivelyselected as sensor electrodes SE. Thus, the total sensor period can bereduced by half. In the present embodiment, a structure of connectingtwo switch lines 79 a adjacent to each other is employed. However, astructure of connecting three or more switch lines 79 a may be employed.

Fifth Embodiment

FIG. 15 is a plan view schematically showing a part of a liquid crystaldisplay device 1 having a touch function according to a fifthembodiment. The display device 1 having a touch detection function isdifferent from that of the first embodiment in terms of the structure ofconnection between switch lines 79 a and 79 b and common electrodes 26,a switch line drive circuit 80, etc. However, the other structures arethe same as those of the first embodiment (FIG. 6B). Thus, the samestructures as those of the first embodiment are denoted by the samereference numbers, descriptions thereof being omitted.

As show in FIG. 15, in the display device 1 of the present embodiment, afirst output terminal from the switch line drive circuit 80 is connectedto switch lines 79 a and 79 a of adjacent rows (first and second rows)of common electrodes 26. In the same manner, a second output terminalfrom the switch line drive circuit 80 is connected to switch lines 79 band 79 b of adjacent rows (first and second rows) of common electrodes26.

In the present embodiment, similarly, in each sensor period, the commonelectrodes 26 in two rows connected to each other can be collectivelyselected as sensor electrodes SE. Thus, the total sensor period can bereduced by half. In the present embodiment, a structure of connectingtwo switch lines 79 a adjacent to each other is employed. However, astructure of connecting three or more switch lines 79 a may be employed.

Sixth Embodiment

FIG. 16 is a plan view schematically showing a part of a liquid crystaldisplay device 1 having a touch function according to a sixthembodiment. The display device 1 having a touch detection function isdifferent from that of the second embodiment in terms of the structureof connection between switch lines 79 a and common electrodes 26, aswitch line drive circuit 80, etc. However, the other structures are thesame as those of the second embodiment (FIG. 10). Thus, the samestructures as those of the second embodiment are denoted by the samereference numbers, descriptions thereof being omitted.

As shown in FIG. 16, in the display device 1 of the present embodiment,a first output terminal from the switch line drive circuit 80 isconnected to switch lines 79 a and 79 a of adjacent rows (first andsecond rows) of common electrodes 26.

In the present embodiment, similarly, in each sensor period, the commonelectrodes 26 in two rows connected to each other can be collectivelyselected as sensor electrodes SE. Thus, the total sensor period can bereduced by half. In the present embodiment, a structure of connectingtwo switch lines 79 a adjacent to each other is employed. However, astructure of connecting three or more switch lines 79 a may be employed.

In FIG. 6B, FIG. 7, FIG. 10 and FIG. 13 to FIG. 16, the structuralelements related to display are omitted such that the sensor functioncan be easily understood. However, the actual device comprises thestructural elements necessary for display as explained in FIG. 3 andFIG. 6A.

Now, this specification explains structural examples of the black matrix8 and a shielding portion 9 usable in each of the above embodiments withreference to FIG. 17. In the display device 1 having a touch detectionfunction, the structures on the first substrate 3 side are the same asthose of the first embodiment. Thus, the same structures as those of thefirst embodiment are denoted by the same reference numbers, descriptionsthereof being omitted. Regarding the second substrate 4, the blackmatrix 8 is extracted, the entire part of the second substrate 4 beingomitted.

As shown in FIG. 17, in the present embodiment, the spacer 7 is providedat a position overlapping select switching element 81 a in a plan view.

The black matrix 8 is provided on the second substrate 4. The blackmatrix 8 is provided at positions overlapping each switch line 79 a,each gate line 20, each data line 21, etc., in order to shield themagainst light. Thus, the black matrix 8 has the shape of a lattice. Theblack matrix 8 comprises the shielding portion 9 at a positioncorresponding to the spacer 7. The shielding portion 9 corresponding tothe spacer 7 is slightly larger than the spacer 7.

In the present embodiment, the select switching element 81 overlaps thespacer 7. The spacer 7 is covered by the shielding portion 9 of theblack matrix 8. Thus, the select switching element 81 is also shieldedby the black matrix 8 against light. As a result, the visibility of theselect switching element 81 is reduced although the select switchingelement 81 is provided in the display area 11.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

For example, in the present embodiment, all of the common electrodes 26arranged in matrix are connected to the select circuit 62 such that eachcommon electrode 26 can be selected as a sensor electrode SE. However,the select circuit 62 may not be provided in one or some of the commonelectrodes 26 such that the common electrodes 26 which do not comprisethe select circuit 62 cannot be selected as sensor electrodes SE.

In the above embodiments, only the common electrodes 26 in one row areselected as the sensor electrodes SE in each sensor period. However, thecommon electrodes in a plurality of rows or all of the rows may beselected as the sensor electrodes SE in series in each sensor period.

In the above embodiments, as the display device 1 and a method ofdriving the display device 1, this specification exemplarily discloses aliquid crystal display device 1 and a method of driving the liquidcrystal display device. However, as the display device 1 of eachembodiment, various flat panel display devices 1 can be considered. Forexample, an organic electro-luminescent display device 1, a differentself-luminous display device 1, and an electronic paper display device 1having an electrophoresis element can be considered. As a matter ofcourse, the above embodiments may be applied to small, medium-sized orlarge display devices without particular limitation.

1. A display device comprising: a plurality of gate lines; a pluralityof data lines intersecting with the gate lines; a plurality of pixelelectrodes provided in areas defined by the gate lines and the datalines; a plurality of common electrodes opposing to the pixelelectrodes; and a pair of third wirings, one of the third wiringsconnected to the corresponding common electrode via a firstsemiconductor switching element and the other third wiring connected tothe corresponding common electrode via a second semiconductor switchingelement, wherein when the first semiconductor switch turns on and thesecond semiconductor switch turns off, the sensor signal is supplied tothe corresponding common electrode via the one of the third wirings,when the first semiconductor switch turns off and the secondsemiconductor switch turns on, the common signal is supplied to thecorresponding common electrode via the other third wiring.
 2. Thedisplay device of claim 1, further comprising, a common signal linewhich has the common signal and a first switch located between thecommon signal line and the other third wiring, an active guard signalline which has an active guard signal and a second switch locatedbetween the active guard line and the other wiring, when the firstsemiconductor switch turns off, the second semiconductor switch turnson, and the first switch turns on and the second switch turns off, thecommon signal is supplied to the corresponding common electrode via theother third wiring, and when the first semiconductor switch turns off,the second semiconductor switch turns on, and the first switch turns offand the second switch turns on, the active guard signal is supplied tothe corresponding common electrode via the other third wiring.
 3. Thedisplay device of claim 2, wherein the active guard signal is the signalwhich has the same phase of the sensor signal.
 4. The display device ofclaim 2, wherein at least the common electrode which is supplied theactive guard signal via the other third wiring is next to the commonelectrode which is supplied the sensor signal via the one of the thirdwiring.
 5. The display device of claim 1, wherein when the firstsemiconductor switch turns off and the second semiconductor switch turnsoff, the corresponding common electrode is set at a floating state. 6.The display device of claim 5, wherein at least the common electrodewhich is in the floating state is next to the common electrode which issupplied the active guard signal via the other third wiring.
 7. Thedisplay device of claim 1, wherein the pair of the third wirings arecrossing the gate lines.
 8. The display device of claim 1, wherein eachof the first semiconductor switch element and the second semiconductorswitch element includes a transistor, a gate of the transistor of thefirst semiconductor switch is connected a first switch line, and a gateof the transistor of the second semiconductor switch is connected asecond switch line, the first switch line and the second switch line arecrossing the pair of the third wirings.
 9. The display device of claim1, wherein the plurality of the pixel electrodes include the pixelelectrode for a red pixel area, the pixel electrode for a green pixelarea, and the pixel electrode for the blue pixel area, and, each of thefirst semiconductor switch element and the second semiconductor switchelement is located in the blue pixel area.